Thesis title: Modelli per la gestione, l’efficientamento e la sostenibilità dei grandi impianti di trattamento acque.
This doctoral thesis has the following main objectives: to develop an integrated model for the life-cycle assessment of wastewater treatment plants, covering the construction, operational management and sludge disposal phases; to apply this model to a real-world case study using bill of quantities data; to develop and validate two dedicated software tools (InfraLCA for the operational phase and ConstructLCA PRO 2025 for the construction phase), updating emission factors in accordance with the most recent scientific sources (IPCC AR5, Ecoinvent v3.8, ISPRA/Ecoinvent 2022 national electricity mix); conduct a systematic parametric sensitivity analysis to identify the parameters with the greatest influence on the plant’s environmental performance and quantify the uncertainty associated with the results.
In order to achieve these objectives, the thesis is structured into eight chapters. Chapter 2 describes the model adopted, with particular reference to ISO 14040/14044 standards, the CML 2001 methodology for impact assessment, and the software tools developed as part of the research, including the critical review conducted on them. Chapter 3 presents the case study in detail, describing the characteristics of the Acqua Pubblica Sabina S.p.A. plant (design capacity 24,000 m³/d, 75,000 PE), the treatment processes adopted and the system boundaries defined for the LCA analysis. Chapter 4 presents the results of the LCA analysis of the operational management phase for the three plant scenarios analysed — conventional activated sludge (Scenario A), MBR system (Scenario B) and anaerobic digestion with photovoltaic integration (Scenario C) — with an in-depth analysis of the GWP, AP and EP impact categories. Chapter 5 presents the LCA analysis of sludge treatment and disposal for four alternative scenarios (landfill, agricultural spreading, incineration with energy recovery, composting). Chapter 6 presents the results of the LCA analysis of the construction phase, including a sensitivity analysis with respect to material emission factors.
Chapter 7 forms the interpretative core of the thesis: it presents an integrated discussion of the complete life cycle, with the three phases consolidated into a single functional unit (1 m³ of treated water, useful life 30 years) and a systematic analysis of the trade-offs between the various plant configurations. The main contribution of the research is the quantification of the integrated lifecycle GWP, equal to 0.655 kgCO₂eq/m³ for the reference scenario with updated parameters and sludge disposal via agricultural spreading, with the operational management phase dominating the balance (87.2%), followed by sludge disposal (8.5%) and depreciated construction costs (4.3%). A systematic parametric sensitivity analysis using the OAT method completes the interpretative framework. Finally, Chapter 8 summarises the main results, describes the research’s original contributions relative to the state of the art, discusses the limitations of the analysis and outlines prospects for future development.